1. Field of the Invention
The present invention relates to a resource utilizing method of refuses so as to remove the refuses such as consumer wastes in urban and rural areas.
2. Relevant Background
Along with social progress, sustainable development has become the goal of the human pursuit. Refuses as the products of human activities have not only become the burden of the earth but also the serious impediment to development of the society. The average annual growth rate of the refuses in the world is 8.42% and that in China is up to 10%. 0.49 billion tons of refuses are produced in the world each year. China alone produces nearly 0.15 billion tons of municipal consumer wastes each year. The accumulated amount of municipal consumer wastes in China has been up to 7 billion tons.
In terms of resource utilization, consumer refuses in urban and rural areas may be classified into two categories. The first category may be called anaerobic decomposition refuses, which consist of the perishable and biodegradable organic matters with higher moisture content and include kitchen garbage, waste wood, waste cotton, waste cotton fabric and so on. Waste pollution mainly results from these refuses, wherein the resources are combustible gases and plant fertilizers. The second category may be called non-anaerobic decomposition refuses, which include recyclable materials such as waste plastics, steel scraps and the like and a small part of earth, ashes, glass, ceramics, construction wastes, etc., wherein the resources are steel scraps, plastics, chemical fibers and so on.
Since the anaerobic decomposition refuses in the organic matters are rich in protein, fat and carbohydrate compounds, NH3, H2S and harmful hydrocarbon gas may be produced during the microbial decomposition process of the organic matters at the normal temperature. These gases have strong odor and toxicity, and directly endanger human. A refuse dump is the place where mosquitoes, flies, rats and insects breed, and is the source of infection of malaria, schistosomiasis, encephalitis B, cholera, viral hepatitis A, dysentery, typhoid fever, hepatitis, plague, leptospirosis and blood-sucking insects' disease. If refuses are piled up casually, CO2, CH4 and the harmful gas H2S may be produced due to the biological action, which may further lead to explosion. Harmful substances in the refuses continue to pollute air, soil and water, and further intrude into the human body via air, soil, water and food as the media or carrier, damaging human health.
The waste disposal methods in the art are as follows.
Now, landfill and incineration are the most commonly used methods of municipal consumer wastes treatment in the world.
1. Landfill
Landfill is a waste treatment method that is used mostly. Its principle is to dump the wastes to a certain height in a given site covered with covering materials so as to make them reach a steady state after long-term physical, chemical and biological actions. Specific methods include a natural stacking method and a sanitary landfill method. The natural stacking method is simple and easy to be carried out, but causes serious environmental pollution. Since the natural stacking method causes serious and long-term pollution of soil and groundwater, it is a negative emergency measure. The sanitary landfill method is a commonly used method of processing a large amount of urban and rural consumer wastes at present. Countries in the world generally adopt the sanitary landfill method. The shortcomings of this method are large occupation area, complex engineering organization and low degree of harmless processing and volume reduction. There is a potential threat of secondary pollution. In particular, the produced biogas is not easy to diffuse, prone to explosion, which may render the resources in the refuses to be wasted. During the operation, odor is produced. Landfill site is often far from the down town, leading to much more transportation cost. The selection of landfill site is also greatly restricted. This method is likely to cause pollution of earth surface and groundwater.
2. Incineration
Incineration is a waste treatment process in which the wastes as solid fuels are put into the incinerator and then the combustible components thereof are intensively reacted with the oxygen in the air at high temperature. During this process, heat is generated and the wastes are turned into combustion gases with high temperature and a small quantity of the solid residues with stable nature. The advantage of incineration is in that a good volume reduction is reached. The volume can be reduced more than 90% and the weight thereof can be reduced more than 80% as the result of residues, obtaining a relatively thorough treatment. The disadvantage of incineration is destruction of resources. The wastes contain about 70% moisture. Aqueous organic matters consume energy and combustible wastes release energy. During incineration, consumed energy neutralizes released energy, and thus residual energy is very little or negative. Therefore, the calorific value of the wastes is highly required. Further, the consumption of fuels, such as coal and oil, wastes a lot of recyclable resources and chlorinated dibenzo dioxins (PCDD) and chlorinated dibenzofurans (PCDF) are produced during incineration, causing air pollution.
In view of the above, refuses are still treated as wastes. This tendentious concept directs people to adopt the above mentioned waste treatment methods, which results in piled up refuses and seriously impacts on human living space.
The inventor considers that the refuses are the most potential for development and inexhaustible resources. Refuses can become a new starting point of the cycle of resources and an important part of the recycling economy. Organic wastes are above 60%-70% of the municipal consumer wastes and are valuable resources. Recently, as the life level of the people improves, the proportion of the organic wastes in the refuses rises. In-depth understanding of the refuses and deepening are important guiding principles for the discovery of handling the refuses in a right way.
Treatment of municipal organic wastes by an anaerobic fermentation method is an effective method for recycling consumer wastes. Recently, various countries in the world have done much research in terms of biogas generation technology related to waste treatment. For example, the United States and other European countries generally utilize the two-step fermentation and extraction method to study municipal waste anaerobic fermentation so as to produce biogas. China also adopts the anaerobic dry fermentation method to deal with municipal wastes, wherein the produced biogas is used as fuel and the fermented organic wastes turn into organic fertilizer.
In the art, the existing anaerobic fermentation method has the following disadvantages:
1. Either the two-step fermentation and the extraction method or the anaerobic dry fermentation method needs to first perform classification of refuses before processing. This is the biggest bottle neck of restricting waste treatment, thereby resulting in poor utility and huge processing cost of the above mentioned methods. Furthermore, the process is not performed thoroughly, and is not suitable for large-scale application.
2. Intermittent anaerobic treatment restrains waste disposal capacity of the waste treatment plant, and thus a larger area is necessary, which cannot adapt to the waste treatment capacity in modern cities at all.
3. Waste plastics, waste fibers and other non-anaerobic wastes in the refuses cannot be recycled, and are hard to be sorted, which causes a tremendous waste.